corposcindosisfandomcom-20200215-history
How Could a Nerve Graft Reversal Ever Work?
by csmess 10.1.04 =How Could a Nerve Graft Reversal Ever Work?= That's an excellent question. The answer is a little complicated, but I think it explains why the results from the nerve grafts have been poor. If we forget about the sympathetic chain for a minute and just think about nerve grafts in the PNS in general it's easier. The sympathetic chain contains ganglia and nerves which complicates the explanation. Nerves and nerve grafts in the Peripheral Nervous System (PNS) The most important fact you need to know up front is the "nerve" is a very specific term. A nerve is a bundle of fibers, each going to a specific place, incased in a sheath. These fibers are actually the long-skinny axon portion of a neuron (nerve cell). Some fibers are myelinated and others are not. Damaged myelinated fibers have the ability to sprout new fibers after they have been damaged. It's this sprouting that people call "regeneration". OK. So, say a nerve in you arm gets cut. If the nerve can be sewn back together within hours of the injury, the axons will sprout and some of the connections are re-made. If there is a gap between the severed ends, they can use an autograft (usually the sural nerve) to bridge the gap. The nerve graft doesn't repair the nerve. I provides a pipe where axons can sprout and reconnect. Damage to the Sympathetic Chain The sympathetic chain is different than the nerve in your arm that drives the muscles of your hand in several important ways. First, is closer to the source (CNS), so the damage causes problems over a wider range. Think about how different it is when the electrical power cable feeding just your house gets cut versus when the power gets cut to the substation that serves a whole section of a city. In one case, only one house is effected, in the other thousands of homes are effected. Second, the sympathetic chain is not a nerve. It is a chain of ganglia connected by short nerve segments. A ganglion is a bundle of nerve cell bodies which, if damaged or destroyed, are gone for good. You have probably been told that you are born with all the brain cells you'll ever have and if you kill any of them they never regenerate. The same principle applies to nerve cells in ganglia. There are different ETS techniques. Some destroy the ganglia and some just destroy just he nerves between the ganglia. There can be no recovery from the former technique, but, theoretically, a nerve graft might work for the latter situations. Clamping falls into the second category. Even though it is theoretically possible that a nerve graft could work when no ganglionectomy has occurred, there are several factors working against it. The most important factor is time. It is a fact that successful nerve grafts on other parts of the body occur mostly when the grafts are done within hours and, at worst, days after injury. The longer the time from injury to repair, the poorer the results. Most sympathetic nerve grafts are being done years after surgery. The other problem with grafting on the sympathetic chain is that the fibers are cut close to the nerve cell body. It has been shown that the closer the damage is to the nerve cell body, the less chance there is for axon sprouting. The third problem with grafting on the sympathetic chain is that the fibers exiting the chain (going to the heart, lungs, sweat gland, etc.) are not myelinated. Non-myelinated fibers do NOT sprout or regenerate. Conclusion If your surgery included a ganglionectomy or if a ganglion was damaged, you are screwed permanently. Nerve grafts will be useless. If you were clamped or if only a small section of the chain was removed between ganglia, there is a theoretical possibility that an autograft might restore some functionality. But, the results from sympathetic nerve grafts so far have been poor. I suspect the reasons lie in the issues stated above as well as the fact that the nerve grafts were placed endoscopically and not sutured. source